Systems and methods for controlling fuel vapor flow in an engine-driven generator

ABSTRACT

An engine-driven generator that controls fuel vapor flow is provided. The engine-driven generator includes an engine having an air intake, wherein the engine is configured to drive a generator. The engine-driven generator also includes a fuel tank coupled to the engine and configured to provide fuel to the engine. The engine-driven generator includes a valve coupled between the air intake of the engine and the fuel tank. The engine-driven generator also includes a control device configured to transition the valve between a first position and a second position. The first position allows fuel vapor to flow between the fuel tank and the air intake of the engine and the second position inhibits the fuel vapor from flowing between the fuel tank and the air intake of the engine.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/805,295 entitled “SYSTEMS AND METHODS FOR CONTROLLING FUEL VAPOR FLOWIN AN ENGINE-DRIVEN GENERATOR” filed Jul. 21, 2015, which is acontinuation of U.S. patent application Ser. No. 13/423,980 entitled“SYSTEMS AND METHODS FOR CONTROLLING FUEL VAPOR FLOW IN AN ENGINE-DRIVENGENERATOR” filed Mar. 19, 2012, now U.S. Pat. No. 9,109,549, which is aNon Provisional Patent Application of U.S. Provisional PatentApplication No. 61/466,317 entitled “Running Loss Emission Control forEngine Driven Welder” filed Mar. 22, 2011, each of which is hereinincorporated by reference in their entirety.

BACKGROUND

The invention relates generally to engine-driven generators, and, moreparticularly, to systems and methods for controlling fuel vapor flow inan engine-driven generator.

Welding is a process that has become increasingly ubiquitous in variousindustries and applications. While such processes may be automated incertain contexts, a large number of applications continue to exist formanual welding operations, which often rely on the use of anengine-driven generator to power the welding process. Engine-drivengenerators typically include internal components, such as electricalcircuitry, a generator, and an engine, which cooperate to produce asuitable power output for the welding operation. Such power outputs maybe alternating current (AC) power or direct current (DC) power,depending on the welding operation being performed. Moreover, the powermay be adapted for particular applications, such as metal inert gas(MIG) welding, tungsten inert gas (TIG) welding, stick welding, and soforth.

A liquid fuel is often used as a combustible material to operate theengine of an engine-driven generator. As will be appreciated, fuel vapormay be generated in the fuel tank under normal operating conditions.Certain configurations of engine-driven generators direct the fuelvapors to a combustion air intake of the engine. However, when fuelvapors are present at the combustion air intake of the engine duringshutdown of the engine-driven generator, the engine-driven generator may“diesel” or “run on.” When this occurs, the engine-driven generator mayoperate undesirably for a period of time (e.g., multiple seconds orminutes). Accordingly, there is a need in the field for systems andmethod to overcome such undesirable operation.

BRIEF DESCRIPTION

In one embodiment, an engine-driven generator includes an engine havingan air intake, wherein the engine is configured to drive a generator.The engine-driven generator also includes a fuel tank coupled to theengine and configured to provide fuel to the engine. The engine-drivengenerator includes a valve coupled between the air intake of the engineand the fuel tank. The engine-driven generator also includes a controldevice configured to transition the valve between a first position and asecond position. The first position allows fuel vapor to flow betweenthe fuel tank and the air intake of the engine and the second positioninhibits the fuel vapor from flowing between the fuel tank and the airintake of the engine.

In another embodiment, a method for controlling fuel vapor flow in anengine-driven generator includes transitioning a valve to a firstposition when an engine of the engine-driven generator begins operating.The first position allows the fuel vapor to flow between a fuel tank ofthe engine-driven generator and an air intake of the engine. The methodalso includes transitioning the valve to a second position when theengine of the engine-driven generator stops operating. The secondposition inhibits the fuel vapor from flowing between the fuel tank ofthe engine-driven generator and the air intake of the engine.

In another embodiment, a portable engine-driven system includes anengine having an air intake. The system also includes a fuel tankcoupled to the engine and configured to provide fuel to the engine. Thesystem includes a solenoid valve coupled between the air intake of theengine and the fuel tank and configured to transition between a firstposition and a second position. The first position allows fuel vapor toflow between the fuel tank and the air intake of the engine and thesecond position inhibits the fuel vapor from flowing between the fueltank and the air intake of the engine.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a perspective view of an embodiment of a portableengine-driven welding generator system which may employ devices forcontrolling fuel vapor flow in accordance with aspects of the presentdisclosure;

FIG. 2 is a pictorial view of an embodiment of a system for controllingfuel vapor flow in an engine-driven generator in accordance with aspectsof the present disclosure;

FIG. 3 is a block diagram of an embodiment of a system for controllingfuel vapor flow in an engine-driven generator using a two-way valve inaccordance with aspects of the present disclosure;

FIG. 4 is a block diagram of an embodiment of a system for controllingfuel vapor flow in an engine-driven generator using a two-way valve withpressure relief in accordance with aspects of the present disclosure;

FIG. 5 is a block diagram of an embodiment of a system for controllingfuel vapor flow in an engine-driven generator using a three-way valve inaccordance with aspects of the present disclosure;

FIG. 6 is a block diagram of an embodiment of an engine-driven generatorsystem having a control device to transition a valve for controllingfuel vapor flow in accordance with aspects of the present disclosure;and

FIG. 7 is a flow chart of an embodiment of a method for controlling fuelvapor flow in an engine-driven generator system in accordance withaspects of the present disclosure.

DETAILED DESCRIPTION

Referring now to the drawings, FIG. 1 illustrates a portableengine-driven welding generator system 10 having a generator 12drivingly coupled to an engine 14 in a single enclosure 16 in accordancewith an exemplary embodiment of the present technique. As discussed indetail below, the system 10 may employ devices for controlling fuelvapor flow. For example, the system 10 may employ devices that allowfuel vapor to flow to the engine 14 while the engine 14 is operating andinhibit fuel vapor from flowing to the engine 14 while the engine 14 isnot operating. Therefore, “dieseling” may be reduced and/or eliminatedby blocking fuel vapors from flowing to the engine 14 at undesiredtimes. As will be appreciated, the disclosed embodiments may be used ina variety of electromechanical systems, including welding systems,non-welding systems, motor-generator systems, and so forth.

As discussed in detail below, the single enclosure 16 includes multiplefunctionalities in one portable system to improve productivity andreduce space consumption. Specifically, the system 10 is configured tooutput electrical power for a variety of applications, includingwelding, cutting, battery charging, jump starting, and so forth.Moreover, the system 10 includes intelligence (e.g., logic in softwareand/or hardware) to adjust the outputs based on various feedback of thesystem 10 and an external device receiving the electrical power from thesystem 10. For example, the system 10 does not randomly provide outputpower for welding and/or charging, but rather the system 10 analyzesvarious parameters, executes various logic, and intakes sensed feedbackto make an intelligent decision regarding the output. In someembodiments, however, the system 10 may provide output power withoutadjustment or analysis of any parameters or feedback. The enclosure 16consists of a front panel 18, a rear panel 20, a right side 22, and aleft side 24, all engaging a base 26 to complete the enclosure 16. Theenclosure 16 protects the engine 14 and the generator 12 from dust,debris, and rough handling. The enclosure 16 also reduces noise andhelps to cool the engine 14 by preventing hot air recirculation via acool air inlet 28 on the front panel 18 by pulling air through theinterior volume of the enclosure 16. In certain embodiments, the rearpanel 20 may also include an air inlet for air intake and/or exhaustflow.

A control system regulates the electrical power supplied by thegenerator 12 and allows for it to be used for a welding process and/orauxiliary power to other devices or tools. The front panel 18 mayinclude various control inputs, indicators, displays, electricaloutputs, and so forth. In one embodiment, the front panel 18 may includevarious indicators 30 to provide feedback to the user. For example, theindicator 30 may include an LCD to display voltage, amperage, airpressure, and the like. Further, in some embodiments, a user input 32may include a touch screen, knobs, and/or buttons configured for a modeof operation, an output level or type, etc. For instance, the user input32 may include a dial rotatable to select a mode of operation, such as aDC weld, an AC weld, a battery charge, or a tool operation. Embodimentsof the front panel 18 include any number of inputs and outputs, such aswelding methods, oil pressure, oil temperature, and system power.

The engine 14 provides output power (e.g., a mechanical output) to drivethe welding generator 12. In certain embodiments, the power from theengine 14 operates the generator 12 via a drive shaft. The drive shaftmay be directly or indirectly coupled to one or more driven mechanisms.For example, an indirect coupling may include a belt and pulley system,a gear system, or a chain and sprocket system. In the presentembodiment, the drive shaft couples directly to the generator 12.However, either arrangement can be used for the connection between theengine 14 and the generator 12.

In an embodiment, the engine 14 may include a combustion engine poweredby gas or diesel, LP fuel, natural gas, or other fuel, and driving oneor more drive shafts. For example, the engine 14 may include anindustrial gas/diesel engine configured to output anywhere from about 9horsepower (Hp) to about 30 Hp. Generally, the weight of such an engine14 may vary with the size and Hp rating of the engine 14. For example, a23 Hp engine may weigh approximately 100 lbs., whereas a similar 9 Hpengine may weigh less than approximately 50 lbs. Thus, the portablesystem 10 may benefit from the use of a smaller engine 14.

As discussed previously, embodiments may include a generator 12 coupledto the engine 14. Thus, the generator 12 may convert the power output(e.g., mechanical energy) of the engine 14 to an electrical power.Generally, the generator 12 includes a device configured to convert arotating magnetic field into an electrical current (e.g., AC generator).The generator 12 includes a rotor (the rotating portion of thegenerator) and a stator (the stationary portion of the generator). Forexample, the rotor of the generator 12 may include the rotating driveshaft of the engine 14 disposed in a single stator configured to createan electrical current (e.g., welding current) from the rotation of themagnetic field. In an embodiment, the generator may include a four-polerotor and three-phase weld output configured to provide beneficialwelding characteristics. Further, the generator 12 may include aplurality of independent winding sections in the rotors and/or stators,such that the generator 12 is configured to output multiple electricaloutputs having different characteristics. For example, the generator 12may include a first section configured to drive a welding current to awelder and a second section configured to drive a current for other ACoutputs. In some embodiments, multiple generators 12 may be connected tothe drive shaft.

As depicted in FIG. 1, the enclosure 16 includes various access panelsto enable servicing, repair, and so forth. For example, a side accesspanel 34 is configured to attach to opposite sides of the enclosure 16.The top of the enclosure 16 includes an access panel or hatch 36, whichare both rotatable between open and closed positions above thecomponents of the system 10. The top hatch 36 can rotate open to enableaccess to the engine 14. Similarly, the side access panel 34 can rotateopen to enable access to the engine 14, oil filter, spark plugs, etc.

The illustrated system 10 also includes various external connections 38.The external connections 38 may include various outlets and couplersconfigured to provide access to the electrical power generated by thesystem 10. For example, the external connections 38 may include an ACpower output and a DC power output, which may be coupled to variousdevices and tools. For example, the AC power output may provideauxiliary power to various devices or tools integrated within or coupledto the system 10. The DC power output can be coupled to various weldingand cutting tools, such as a welding torch. The welding devices mayreceive current from the generator 12 via the external connections 38.As will be appreciated, the torch may include various welding devices,such as a TIG (tungsten inert gas) torch, a MIG (metal inert gas) gun,or a plasma cutting torch. The system 10 may also include welding cableconnecting the torch to the external connections 38. Further, the system10 may include other components necessary for operation of a weldingdevice, such as a wire feeder, a shielding gas supply, and/or any othercomponent, or combination thereof. The system 10 also includes a fueltank that holds fuel to be provided to the engine 14. The fuel tankincludes an opening for adding fuel to the fuel tank. A fuel cap 40 isused to cover the opening of the fuel tank and may be used to vent fuelvapor. For example, the fuel cap 40 may include a pressure relief valvefor releasing fuel vapor when pressure within the fuel tank exceeds athreshold pressure.

FIG. 2 is a pictorial view of an embodiment of a system 42 forcontrolling fuel vapor flow in the engine-driven generator 10 (or in anyengine-driven system, such as portable engine-driven systems). Thesystem 42 includes a fuel tank 44 for holding fuel 46 (e.g., generallyliquid fuel) that is provided to the engine 14 and is used to power theengine 14. As will be appreciated, fuel vapor of the fuel 46 may collectin and contact an upper portion 48 (e.g., vapor space) of the fuel tank44. The upper portion 48 may act as an accumulator for fuel vapor. Incertain embodiments, the volume of the upper portion 48 may beapproximately 5 to 20% of the total fuel tank 44 volume. The fuel cap 40covers an opening used for filling the fuel tank 44 with the fuel 46. Toinhibit fuel vapor from freely flowing into the atmosphere, the fuel cap40 may generally seal the opening (e.g., the fuel cap 40 may not includeapertures that allow fuel vapor to freely flow out of the fuel tank 44).A neck tube 50 extends from the fuel cap 40 and may be used to helpdetermine the recommended amount of liquid fuel 46 in the fuel tank 44to allow for thermal expansion of the fuel 46.

A valve 52 may be used to direct fuel vapor from the fuel tank 44 (e.g.,the upper portion 48 of the fuel tank 44) to the engine 14. Asillustrated, the valve 52 may be coupled to the upper portion 48 of thefuel tank 44. Further, a hose 54 couples the valve 52 to an air intake56 of the engine 14. The engine 14 may combust fuel vapor from the fueltank 44 and inhibit the fuel vapor from being vented (e.g., escapingfrom the system 42) to the atmosphere, such as while the engine 14 isoperating. For example, the valve 52 may be closed (e.g., to inhibitfuel vapor from flowing to the engine 14) while the engine 14 is notoperating and the valve 52 may be opened (e.g., to enable fuel vapor toflow to the engine 14) while the engine 14 is operating. The valve 52may be any suitable valve and may be controlled by any suitablecontrolling mechanism of the engine-driven generator 10. In certainembodiments, the fuel cap 40 may include a pressure relief portion torelieve vapor pressure buildup in the fuel tank 44, such as for timeswhile the engine 14 is not operating. In some embodiments, the valve 52may also include a pressure relief portion to relive vapor pressurebuildup in the fuel tank 44. As described, the system 42 may be used toprovide fuel vapor to the engine 14 when desired. Accordingly, fuelvapor may be inhibited from flowing to the engine 14 at undesirabletimes (e.g., such as while shutting off the engine-driven generator 10).Therefore, undesirable behavior, such as “dieseling” may be reducedand/or eliminated.

FIG. 3 is a block diagram of an embodiment of a system 58 forcontrolling fuel vapor flow in the engine-driven generator 10 using atwo-way valve 52. As illustrated, one embodiment of the valve 52 isdepicted. The valve 52 includes a default position 60 and a controlledposition 62. In the default position 60, fuel vapor flow between thefuel tank 44 and the engine 14 is blocked. In the controlled position62, fuel vapor may flow between the fuel tank 44 and the engine 14.Specifically, fuel vapor may flow through the valve 52 and the hose 54to the air intake 56 of the engine 14.

Force applied by a spring 63 holds the valve 52 in the default position60. The force of the spring 63 may be overcome by energizing a solenoid64 to transition the valve 52 to the controlled position 62. As will beappreciated, as long as the solenoid 64 is energized, the valve 52 willbe held in the controlled position 62. The solenoid 64 may be energizedby any suitable device of the engine-driven generator 10, as explainedin detail below. A valve inlet 66 and a valve outlet 68 allow the fuelvapor to flow through the valve 52 (e.g., when the valve 52 is in thecontrolled position 62).

As discussed above, the fuel cap 40 may include a pressure relief valve70. As such, fuel vapor pressure may flow through a pilot line 72. Whenthe force applied via the pilot line 72 is greater than the forceapplied by a spring 74, fuel vapor may be released from the fuel tank 44and flow to an external outlet 76. The external outlet 76 may be anopening to the atmosphere or a connection to a storage container used tostore fuel vapor, for example. As will be appreciated, the pressurerelief valve 70 may provide enhanced safety to the system 58 to inhibitexcessive pressure buildup within the fuel tank 44. For example, thepressure relief valve 70 may be configured to vent or release fuel vaporwhen pressure within the fuel tank 44 exceeds a safety threshold such as0.5, 1.0, 3.0, or 5.0 PSI.

The valve 52 may be configured to be in the default position 60 whilethe engine 14 is not operating. Further, the valve 52 may be configuredto be in the controlled position 62 while the engine 14 is operating.Accordingly, pressure will not generally build within the fuel tank 44while the engine 14 is operating because the valve 52 is in thecontrolled position 62. Therefore, the pressure relief valve 70 willgenerally operate while the engine 14 is not operating and the valve 52is in the default position 60.

FIG. 4 is a block diagram of an embodiment of a system 78 forcontrolling fuel vapor flow in the engine-driven generator 10 using atwo-way valve 52 with pressure relief. Although the two-way valve 52 isintegrated with the pressure relief, in certain embodiments, thepressure relief may be separate from the two-way valve 52. As will beappreciated, the two-way valve 52 with pressure relief may be considereda three-way valve. In the present embodiment, the valve 52 includes adefault position 80 and a controlled position 82. In the defaultposition 80, fuel vapor flow between the fuel tank 44 and the engine 14is blocked. In the controlled position 82, fuel vapor may flow betweenthe fuel tank 44 and the engine 14 (e.g., from the valve inlet 66 to thevalve outlet 68). Specifically, fuel vapor may flow through the valve 52and the hose 54 to the air intake 56 of the engine 14. Furthermore, fuelvapor may flow from the air intake 56 to a carburetor 84 of the engine14. In other embodiments, fuel vapor may flow from the air intake 56 toa fuel injection system of the engine 14.

Force applied by the spring 63 holds the valve 52 in the defaultposition 80. The force of the spring 63 may be overcome by energizingthe solenoid 64 to transition the valve 52 to the controlled position82. As will be appreciated, as long as the solenoid 64 is energized, thevalve 52 will be held in the controlled position 82. The solenoid 64 maybe energized by any suitable device of the engine-driven generator 10,as explained in detail below. The valve 52 also includes a pilot 85 thatprovides force to transition the valve 52 and to release pressure. Theforce applied by the pilot 85 may move the valve 52 a sufficient amountto enable fuel vapor to flow between the inlet port 66 and a relief port86. The fuel vapor may exit the system 78 via an external outlet 88. Theexternal outlet 88 may be an opening to the atmosphere or a connectionto a storage container used to store fuel vapor, for example.

As illustrated, the system 78 may include the pressure relief valve 72to operate in conjunction with the valve 52. For example, in certainembodiments, the pressure relief valve 72 may be configured to vent orrelease fuel vapor at a low or safety threshold pressure (e.g., 0.2 to4.5 PSI). Further, the valve 52 may be configured to vent or releasefuel vapor at a threshold pressure greater than the pressure reliefvalve 72. For example, the valve 52 may be configured to vent or releasefuel vapor at a threshold pressure of between 5.0 and 10.0 PSI.Accordingly, if the pressure relief valve 72 does not release fuel vaporwhen expected, the valve 52 may operate as a backup pressure relief toinhibit over-pressurization from occurring.

FIG. 5 is a block diagram of an embodiment of a system 90 forcontrolling fuel vapor flow in the engine-driven generator 10 using athree-way valve 52 that directly enables flow from the inlet port 66 tothe relief port 86, or from the inlet port 66 to the outlet port 68. Asillustrated, the valve 52 includes a default position 92 and acontrolled position 94. In the default position 92, fuel vapor may flowbetween the fuel tank 44 and the external outlet 88, while fuel vaporflow between the fuel tank 44 and the engine 14 is blocked. In thecontrolled position 94, fuel vapor may flow between the fuel tank 44 andthe engine 14 (e.g., from the valve inlet 66 to the valve outlet 68),while fuel vapor flow between the fuel tank 44 and the external outlet88 is blocked. Specifically, fuel vapor may flow through the valve 52and the hose 54 to the air intake 56 of the engine 14. In such aconfiguration, fuel vapor may selectively be directed to either theexternal outlet 88 or the engine 14 without pressure buildup within thesystem 90.

FIG. 6 is a block diagram of an embodiment of an engine-driven generatorsystem 96 having a control device 98 to transition the valve 52 forcontrolling fuel vapor flow. The control device 98 may be configured tocause the valve 52 to change between a default and controlled positionin order to control the flow of fuel vapor between the fuel tank 44 andthe engine 14. For example, the control device 98 may be configured toenable fuel vapor flow between the fuel tank 44 and the engine 14 in anyof the following conditions: while the engine 14 is operating, while akey is inserted into an ignition switch, while an ignition switch isturned to an operating state, while an oil pressure is greater than athreshold pressure, while an engine temperature is greater than athreshold temperature, and so forth. The control device 98 may includeany suitable hardware and/or software. For example, the control device98 may include one or more processors, memory devices, storage devices,executable code, circuitry, or any combination thereof.

When the control device 98 determines that the valve 52 should beswitched from the default position to the controlled position, thecontrol device 98 may close a switch 100 (e.g., in other embodiments,the control device 98 may open the switch 100). It should be noted thatthe switch 100 may be any type of suitable switching device (e.g., aphysical switch, a solid state device, etc.). With the switch 100closed, a circuit 102 connected to the solenoid 64 becomes complete.Accordingly, a voltage from a voltage source 104 is applied to thesolenoid 64 to energize the solenoid 64 and change the position of thevalve 52. As will be appreciated, the solenoid 64 may be deenergized byopening the switch 100 of the control device 98. As such, the controldevice 98 may control when fuel vapor may flow between the fuel tank 44and the engine 14.

FIG. 7 is a flow chart of an embodiment of a method 106 for controllingfuel vapor flow in the engine-driven generator system 10. Theengine-driven generator system 10 may be configured to transition thevalve 52 to a first position (e.g., controlled position 62, 82, 94) whenthe engine 14 begins operating (block 108). In the first position, fuelvapor may flow between the fuel tank 44 and the air intake 56 of theengine 14. In certain embodiments, the valve 52 may be transitioned tothe first position when an oil pressure of the engine 14 or an ignitionswitch of the system 10 indicates that the engine 14 is operating.Furthermore, the engine-driven generator system 10 may be configured totransition the valve 52 to a second position (e.g., default position 60,80, 92) when the engine 14 stops operating (block 110). In the secondposition, fuel vapor may be blocked or inhibited from flowing betweenthe fuel tank 44 and the air intake 56 of the engine 14. In certainembodiments, the engine-driven generator system 10 may be configured totransition the valve 52 to a third position when a vapor pressure of thefuel vapor exceeds a threshold pressure (block 112).

Technical advantages of the engine-driven generator system 10 asexplained above may include the following. The system 10 may direct fuelvapor to be used for engine 14 combustion while the engine 14, or system10, is operating. In certain circumstances, such a system 10 may complywith regulatory agency requirements (e.g., Environmental ProtectionAgency (EPA)). Further, the system 10 as described herein may decreaseor eliminate the occurrence of fuel vapor accumulation within the system10. In addition, the occurrence of “dieseling” or “engine run on”conditions may be decreased or eliminated.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

The invention claimed is:
 1. An engine-driven generator comprising: anengine having an air intake passage and coupled to a generator, whereinthe engine is configured to drive the generator; a fuel tank coupled tothe engine and configured to provide fuel to the engine; a valvepositioned along a fuel vapor path between the air intake passage of theengine and the fuel tank, wherein the valve comprises a first positionand a second position, and wherein the first position allows fuel vaporto flow from the fuel tank to the air intake passage of the engine viathe fuel vapor path and the second position directly inhibits the fuelvapor from flowing from the fuel tank to the air intake passage of theengine and directly causes the fuel vapor to divert from the fuel vaporpath and to an external outlet; and a control device communicativelycoupled to the valve and configured to cause the valve to transitionbetween the first position and the second position and thereby controlwhen fuel vapor may flow between the fuel tank and the engine.
 2. Theengine-driven generator of claim 1, wherein the control device isconfigured to cause the valve to transition between the first positionand the second position based on a parameter of the engine.
 3. Theengine-driven generator of claim 2, wherein the parameter of the engineis an operating state of the engine.
 4. The engine-driven generator ofclaim 1, wherein the control device is configured to cause the valve totransition between the first position and the second position via asolenoid associated with the valve.
 5. The engine-driven generator ofclaim 4, wherein the control device comprises a switch configured tocontrol a state of a circuit connected to the solenoid.
 6. Theengine-driven generator of claim 5, wherein the switch is a physicalswitch.
 7. The engine-driven generator of claim 5, wherein the switch isa solid state device.
 8. The engine-driven generator of claim 5, whereinthe circuit is connected to the solenoid and to a voltage source.
 9. Theengine-driven generator of claim 8, wherein the switch, in a firststate, is configured to complete the circuit to enable a voltage fromthe voltage source to be applied to the solenoid and thereby change theposition of the valve.
 10. The engine-driven generator of claim 9,wherein the switch, in a second state, is configured to deenergize thesolenoid by opening the circuit.
 11. The engine-driven generator ofclaim 1, wherein the first position of the valve is a controlledposition of the valve and the second position is a default position ofthe valve such that when the valve is in the default position, fuelvapor flow between the fuel tank and the air intake passage of theengine is blocked.
 12. The engine-driven generator of claim 11, whereinthe valve comprises a spring configured to hold the valve in the defaultposition, and a solenoid capable of being energized to overcome a forceof the spring and thereby move the valve to the controlled position, andwherein the solenoid is not energized when the engine is not operatingand is energized when the engine is operating.
 13. The engine-drivengenerator of claim 1, wherein the engine, the fuel tank, and thegenerator are a part of a portable unit having an enclosure surroundingthe engine, the fuel tank, and the generator.
 14. A method forcontrolling fuel vapor flow in an engine-driven generator, theengine-driven generator comprising an engine having an air intakepassage and coupled to a generator, wherein the engine is configured todrive the generator, a fuel tank coupled to the engine and configured toprovide fuel to the engine, and a valve positioned along a fuel vaporpath between the air intake passage of the engine and the fuel tank, themethod comprising: transitioning the valve to a first position to allowfuel vapor to flow between the fuel tank and the air intake passage ofthe engine; and transitioning the valve to a second position, the secondposition of the valve directly inhibiting the fuel vapor from flowingbetween the fuel tank and the air intake passage of the engine.
 15. Themethod of claim 14, wherein transitioning the valve to the firstposition comprises transitioning the valve to the first position using acontrol device communicatively coupled to the valve.
 16. The method ofclaim 15, comprising transitioning the valve to the second position,using the control device, while the engine-driven generator is shuttingoff to reduce or eliminate dieseling of the engine.
 17. The method ofclaim 15, comprising transitioning the valve to the first position,using the control device, when the engine of the engine-driven generatorbegins operating.
 18. The method of claim 17, wherein transitioning thevalve to the first position when the engine of the engine-drivengenerator begins operating comprises transitioning a two-way valve fromthe second position to the first position, the two-way valve beingpositioned on an upper part of the fuel tank where the fuel vaporaccumulates.
 19. A portable engine-driven system comprising: an enginehaving an air intake passage; a fuel tank coupled to the engine andconfigured to provide fuel to the engine; a three-way valve positionedalong a fuel vapor path extending between the air intake passage of theengine and the fuel tank, wherein the three-way valve comprises aninlet, a first outlet, and a second outlet, the inlet being configuredto receive fuel vapor from the fuel tank, the first outlet beingconfigured to provide the fuel vapor to the air intake passage of theengine, and the second outlet being configured to provide the fuel vaporonly to the atmosphere or to a storage container, wherein the three-wayvalve is configured to transition between a first position and a secondposition, wherein the first position allows fuel vapor to flow betweenthe fuel tank and the air intake passage of the engine, and the secondposition allows fuel vapor to flow between the fuel tank and theatmosphere or the storage container; and a control devicecommunicatively coupled to a solenoid associated with the three-wayvalve, wherein the solenoid is configured to cause the three-way valveto transition between the first position and the second position inresponse to command signals from the control device.